2.3 congenital anomalies Flashcards
(60 cards)
highest frequencies of death under 1 year
congenital mlaformation, deformation, and chromosomal abnormalities, disorders related to short gestation and low birth weight, sudden infant death syndrome (SIDS)
congenital anomalies
morphological defects present at birth, may not be expressed until later in life, can or cannot be genetic defect, 3% of newborns have a major anomaly (cosmetic or functional significance), most common cause of death in first year of life, significant cause of mortality and morbidity in all early years of life, in reality, observed anomalies in live births represent the leaset serious that occur
malformations
primary error of morphogenesis with intrinsic abnormal development (anencephaly, congenital heart defects). Multifactorial. Single/multiple
disruptions
secondary destruction of organ/body region that was previously normal in development. Extrinsic distrubance (amniotic bands that compress portions of fetus)
Anencephaly
neural tube defect with absence of cerebral hemisphere, skull, and skin
cleft lip/palate
if isolated - compatible with life, with malformation syndrome - severe cardiac defects
deformations
like disruptions these are due to extrinsic disturbance as a localized/generalized fetal compression by biomechanical forces –> structural anomalies (uterine constraint, oligohydramnios) –>(club feet)
Sequence
cascade of anomalies triggered by one initiating event
Potter sequence of oligohydramnios
renal agenesis, amniotic leak, maternal HTN, toxemia (U/O insff) —-> all lead to oligo hydramnios —–>can lead to amnion nodosom (plaques of squamous cells and fibrin), pulmonary hypoplasia, and fetal compression —-> fetal compression can lead to pulmonary hypoplasia, altered facies, positioning defects of feet and hands, breech presentation
syndrome
a constellation of congenital anomalies that are thought to be pathologically related but unlike a sequence can not be explained by a single initiating event. Can have a single etiology, eg a viral disease or chromosomal alteration that affects different tissues
Causes of anomalies
genetic, environmental and multifactorial (50 - 75% unknown)
genetic causes of congenital anomalies
chromosomal (karyotypic) abberations, single gene mutsionts
karyotypic abberations
10-15% of CA
when do most karyotypic abberations occur
during gametogenesis (not familial)
ex of karyotypic abberation
Down’s a la Robertsonian translocation of 21 with another chromosome (4%)
karyotypic abberations and death
80-90% of chromosomal number abberations die in the uterus
single gene mutations inheritance
90% AD or AR and 10% X-linked
examples of loss of fn genes involved in normal organogenesis
sonic hedgehog - holoprosencephally, HOXGL13 - digit anomalies (polydactyly, syndactyly)
holoprosencephaly
incomplete separation of cerebral hemispheres across the midline
syndactyly
fused fingers
Environmental causes of CA
viral infections, drugs and chemicals, radiation, maternal diabetes
most common viral infections in CA
rubella, CMV (MOST COMMON - most asymptomatic)
risky period to contract rubella
conception to 16 weeks
incidence of rubella
50% 1st month, 20% 2nd, 7% 3rd
